We said in the previous mitzvah that debts owed to us by other Jews are to be considered voided by the Shemittah year. Not so when it comes to loans we may have made to non-Jews. Not only are they not canceled by the Sabbatical year, the Torah tells us to actively pursue repayment.
This makes sense, since debts we owe other Jews are canceled while those we owe non-Jews are not. Really, it just reflects a level playing field with both Jews and non-Jews; everything comes out in the wash. To forgive debts owed by non-Jews when there is no reciprocal forgiveness of debts owed to them would kind of make one a sucker, or at the very least a very poor businessman. Nevertheless, the Sefer HaChinuch ascribes a deeper meaning to this mitzvah. He sees it as one of those things that helps keep the Jews separate and distinct. There’s an aspect of anti-assimilation in ensuring that we must treat Jews and non-Jews differently. (Please note that even though we treat the two groups differently, we still treat each group equitably.)
This mitzvah applies all times and places. It is discussed in the Midrash in the Sifre and is codified in the Mishneh Torah in the first chapter of Hilchos Malveh v’Loveh. This mitzvah is #142 of the 248 positive mitzvos in the Rambam’s Sefer HaMitzvos; it is not listed in the Sefer HaMitzvos HaKatzar of the Chofetz Chaim. The Ramban (Nachmanides) does not count this among the 613 mitzvos, saying that it is merely a statement in contradistinction to the way we must treat Jews, as outlined in Mitzvah #475.